(1) Field of the Invention
The present invention relates to a data broadcast apparatus which multiplexes data of a TV program and additional data for the TV program and broadcasts them. The invention in particular relates to techniques for controlling reproduction of additional data in a reception apparatus when, for instance, a TV program which is being broadcast is interrupted for a TV program of higher priority.
(2) Related Art
In recent digital broadcasting, additional data such as character information is multiplexed with program data such as video and audio and broadcast.
In general, the same or renewed additional data is repeatedly multiplexed with program data and broadcast, with a cycle of about 5 to 10 seconds.
A data broadcast apparatus that performs such digital broadcasting is disclosed in Japanese Laid-Open Patent Application No. H10-313449.
The most common method used for periodic broadcast of additional data is the Data Carousel (hereafter simply called “carousel method”) specified by the internationally standardized DSM-CC (Digital Storage Media—Command and Control) (described in detail in Information Technology—Generic Coding of Moving Pictures and Associated Audio: DSM-CC-ISO/IEC 13818-6). Broadcast of additional data according to the carousel method has been adopted for BS digital broadcasting service and the like in Japan (described in detail in the ARIB STD-B24 specification “Data Broadcast Coding and Transmission in Digital Broadcasting”).
With this method of repeatedly transmitting additional data, a reception apparatus can receive only necessary additional data and reproduce it, with it being possible to utilize enormous amounts of information without a large-capacity memory.
Here, while additional data relating to a TV program is being broadcast by the carousel method, an interruption by an important news program may occur, or the additional data may be found to contain improper content. In such cases, it is desirable to stop the presentation of the additional data to a viewer immediately.
However, even when the data broadcast apparatus stops broadcasting the additional data at once, it does not necessarily mean that the reception apparatus will stop presenting the additional data to the viewer immediately.
The reason for this is as follows. Since the reception apparatus stores the additional data being broadcast by the data broadcast apparatus into a memory and reproduces the additional data stored in the memory, even when no longer receiving the additional data, the reception apparatus continues to reproduce the additional data as long as it is present in the memory.
Also, the additional data may contain a link to other additional data, so that the viewer who is viewing the additional data can jump to the other additional data by selecting, with a remote control or the like, a button included in the additional data to provide a link to the other additional data. The details on this are shown in the ARIB STD-B24 specification “Data Broadcast Coding and Transmission in Digital Broadcasting”.
Here, if the other additional data to which the viewer has jumped contains a button providing a link to the additional data the broadcast of which has stopped, the viewer may select that button and thereby cause an error in the reception apparatus.
To prevent this, when it is necessary to stop presentation of additional data immediately, instead of the additional data the conventional data broadcast apparatus broadcasts additional data called “trouble slide” which merely presents an insignificant message such as “Please Wait for a Moment”, so that the reception apparatus replaces the additional data stored in the memory with this additional data to immediately stop presenting the additional data the broadcast of which has been stopped (described in detail in Japanese Laid-Open Patent Application No. H10-264647).
However, presenting such an insignificant message just to stop presentation of additional data not only causes a great deal of inconvenience to the viewer, but also wastes the transmission band for broadcasting the trouble slide.